How do drops evaporate?

We consider evaporation of pure liquid drops on a thermally conductive substrate. Two evaporative models are considered: one that concentrates on the liquid phase in determining evaporative flux, and the other one that centers on the gas/vapor phase. A single governing equation for the evolution of drop thickness, including both models, is developed. Experiments are used to estimate relevant parameters. We show how the derived governing equation can be used to predict which evaporation model is appropriate under considered experimental conditions.